[CATS-2: a model to predict accumulation of
contaminants in sediment areas.]

Abstract:

CATS is an acronym for Contaminants in Aquatic and Terrestrial
ecoSystems. CATS models have been developed for the prediction of fate
and risks of toxicants. The aim of these models is to predict future
risk levels of toxic substances for food webs. CATS-2 describes the
behaviour of toxicants in sedimentation areas of main rivers in the
Netherlands, such as Hollands Diep, Haringvliet and Ketelmeer.
Bio-availability of toxicants to aquatic organisms is influenced by many
biotic and abiotic characteristics of an ecosystem. Therefore, we
integrated fate of toxicants in the abiotic environment with a food web
model based on biomass cycling. Cycling of organic matter is the
backbone of the model, acting as carrier for the toxicant. The food web
consists of algae, zooplankton, bivalves, chironomid larvae, tubificid
worms, whitefish, predatory fish, benthivorous fish, diving ducks and
fish eating birds (Fig. 1). Cadmium and lindane (gamma-HCH) were
selected to predict future risk levels in an example ecosystem, the
Hollands Diep/Haringvliet area. Risk levels were calculated for two
situations. First for the year 2000, with no additional clean-up of the
river Rhine, and second for the year 2000 with additional clean-up
according to the Rhine Action Programme. Model calculations predict that
risks for both cadmium and lindane decrease, caused by the improvement of
water quality in the River Rhine that feeds the area. The high cadmium
load of the river Rhine in the past is responsible for high cadmium
concentrations in the sediment. Even with additional clean up, sediment
quality does not meet the Dutch quality objective of 2 mg/kg d.w. in the
year 2000. Except for benthivorous fish, risks for the food web are low
in the year 2000 indicating that in general the Rhine Action Plan is
successful if its original emission-reduction goals can be
achieved.

CATS is an acronym for Contaminants in Aquatic and Terrestrial
ecoSystems. CATS models have been developed for the prediction of fate
and risks of toxicants. The aim of these models is to predict future
risk levels of toxic substances for food webs. CATS-2 describes the
behaviour of toxicants in sedimentation areas of main rivers in the
Netherlands, such as Hollands Diep, Haringvliet and Ketelmeer.
Bio-availability of toxicants to aquatic organisms is influenced by many
biotic and abiotic characteristics of an ecosystem. Therefore, we
integrated fate of toxicants in the abiotic environment with a food web
model based on biomass cycling. Cycling of organic matter is the
backbone of the model, acting as carrier for the toxicant. The food web
consists of algae, zooplankton, bivalves, chironomid larvae, tubificid
worms, whitefish, predatory fish, benthivorous fish, diving ducks and
fish eating birds (Fig. 1). Cadmium and lindane (gamma-HCH) were
selected to predict future risk levels in an example ecosystem, the
Hollands Diep/Haringvliet area. Risk levels were calculated for two
situations. First for the year 2000, with no additional clean-up of the
river Rhine, and second for the year 2000 with additional clean-up
according to the Rhine Action Programme. Model calculations predict that
risks for both cadmium and lindane decrease, caused by the improvement of
water quality in the River Rhine that feeds the area. The high cadmium
load of the river Rhine in the past is responsible for high cadmium
concentrations in the sediment. Even with additional clean up, sediment
quality does not meet the Dutch quality objective of 2 mg/kg d.w. in the
year 2000. Except for benthivorous fish, risks for the food web are low
in the year 2000 indicating that in general the Rhine Action Plan is
successful if its original emission-reduction goals can be
achieved.